Endophyte-free Research Articles

Grazing Induces a Patterned Selection Response in Tall Fescue

Pastures with perennial grass species are continuous in stands and are subjected to continual and often intensive natural selective forces. The objective of this study was to investigate the characteristics of tall fescue (Festuca arundinacea Schreb.) cultivars in response to natural selective forces. Ungrazed survivors from four cultivars—endophyte free (EF) GA‐5, endophyte infected (El) GA‐5, Johnstone, and KY‐31—were collected randomly from four paddocks. These paddocks were then grazed at 2.50, 3.75, 5.00, and 6.25 animals ha−1 for 2 yr and grazed survivors collected in similar fashion. These two groups were compared for four whole‐plant, four tiller, and three flag leaf traits in a 2‐yr study along with plants grown directly from the original seed lots. Each cultivar × age group × paddock combination consisted of 42 spaced plants. Each replicate of the original experiment was represented by seven plants selected at random from among the 10 originally collected from each replicate × paddock × entry combination. A polynomial response in grazed survivors was fitted with coefficients of determination ranging from 0.36 (maturity) to 0.79 (tiller number and dry matter yield). Comparison of GA‐5 EF and GA‐5 E1 revealed the influence of endophyte removal on host plants, which was more pronounced after grazing of the paddocks. Endophyte‐infected grazed survivors were late maturing with longer and increased number of tillers and higher dry matter yields. The implications of this research for forage breeding are that (i) the seeded cultivar evaluated under grazing may be different from the original seed lot, and (ii) cultivars are dynamic entities that change over time.

Oral and parenteral vaccination of mice with protein-ergotamine conjugates and evaluation of protection against fescue toxicosis

Acremonium coenophialum produces ergopeptide alkaloids in tall fescue ( Festuca arundinacea Schreb.). These ergot alkaloids decrease serum alkaline phosphatase (ALP) activity, serum cholesterol and prolactin concentrations, as well as average daily gains (ADG) in cattle. The objective of this study was to evaluate the protection of anti-ergotamine antibodies induced by either oral or parenteral vaccination with protein-ergotamine conjugates or passive vaccination with anti-ergovaline, monoclonal antibodies in a murine model of fescue toxicosis. Ergotamine (EG) was conjugated to bovine serum albumin (BSA) and cholera toxin subunit B (CTB) by the Mannich reaction. Mice were blocked based on weight and randomly allocated into five groups of 10 mice each. Treatment groups were as follows: (1) group vaccinated intraperitoneally (ip) with a BSA–EG conjugate and fed an endophyte-infected (EI) fescue diet (BSA–EG group); (2) group orally vaccinated with a CTB–EG conjugate mixed with free cholera toxin (CT) and fed an EI fescue diet (CTB–EG group); (3) nonvaccinated group fed an EI fescue diet (EI group); (4) group passively vaccinated with anti-ergovaline, monoclonal antibodies and fed an EI fescue diet (MoAB group); and (5) nonvaccinated group fed an endophyte-free (EF) fescue diet (EF group). The EI diet contained 1.5 ppm of Ergovaline (EV), whereas no EV was detected in the EF diet. Respective diets were similar upon nutritional analysis. Unvaccinated mice in the EI group exhibited features of fescue toxicosis as indicated by decreased serum ALP activity and cholesterol, and decreased weight gain as compared to mice in the EF group. Antibodies against EG and EV were present in sera of mice in the BSA–EG and MoAB groups, respectively. Mice orally vaccinated with the CTB–EG conjugate developed secretory IgA (sIgA) antibodies and short-lived, systemic IgG responses against EG. Weight gains were increased in the BSA–EG and CTB–EG groups and tended to be increased in the MoAB group vs. the unvaccinated EI group. Serum ALP activity was decreased in the BSA–EG and MoAB groups as compared to the EF group. Serum ALP activity was further decreased in the BSA–EG vaccinated group as compared to the EI group. Cholesterol concentrations were decreased in the EI, BSA–EG and MoAB groups as compared to the EF group. Prolactin concentrations were similar in all groups.

Evaluation of humoral immune responses in cattle grazing endophyte-infected or endophyte-free fescue

Anecdotal reports suggest cattle with fescue toxicosis may not respond to vaccination and thus, experience increased incidence of Bovine Respiratory Disease Complex (BRDC) when shipped to feedlots. Fescue toxicosis causes hypoprolactemia in cattle. Hypoprolactemia decreases humoral immune responses in mice. Therefore, a study was conducted to compare the magnitude of primary and secondary humoral immune responses against specific antigens in cattle grazing endophyte-infected or endophyte-free fescue. Angus steers were blocked by weight and allocated into four groups. Two groups grazed endophyte-infected (EI) fescue and the other two groups grazed endophyte-free (EF) fescue. All steers were injected IM on d 0 and 21 with lysozyme without adjuvant and concanavalin A (Con A) with sheep red blood cells (SRBC) in incomplete adjuvant of Freund. Steers were bled on days 0, 21 and 35 post-vaccination. Average daily gains (ADG), alkaline phosphatase (ALP) activity, cholesterol concentrations, rectal temperatures, and serum prolactin concentrations were measured to confirm fescue toxicosis in steers grazing EI fescue. Antibodies to Con A and SRBC were determined by ELISA and hemagglutination assay, respectively. The ADG were decreased for the EI group during the first month. Rectal temperatures were elevated and serum prolactin concentrations were decreased in the EI group. Cholesterol and ALP concentrations also were decreased in the EI group. Primary and secondary immune responses against Con A tended to be increased and were increased against SRBC in the EI group. Antibodies against lysozyme were not induced in either group. In conclusion, cattle grazing EI fescue mounted similar humoral immune responses to vaccination, despite hypoprolactemia, as cattle grazing EF fescue. Increases in bovine respiratory disease in cattle maintained on EI fescue probably is not associated with lack of humoral immune response to vaccination protocols as a result of fescue toxicosis.

Drought Avoidance Characteristics of Diverse Tall Fescue Cultivars

In recent years, turf type tall fescues (Festuca arundinacea Schreb.) are being used for northern to mid‐South climates in the USA. Limited information is available on the diversity among cultivars of drought resistance and avoidance characteristics, which are important for persistence under drought and high‐temperature stresses. Four cultivars (‘Rebel H’, ‘Rebel Jr.’, ‘Kentucky 31’, ‘Bonsai’) and ‘GA‐5’ endophyte‐free (EF) and endophyte‐infected (El) with Acretnonium coenophialura Morgan‐Jones and Gams were evaluated in a field study at Griffin, GA, (using a clayey, kaolinitic, thermic Typic Haphidult soil) for intraspecific differences in overall drought resistance and for drought avoidance characteristics. These grasses provided a range in morphological traits. Overall drought resistance ranking based on decline in turf quality, leaf firing (LF), and/or wilt expression during dry‐down was Rebel II (best) > Rebel Jr., Kentucky 31, GA‐5‐EF, GA‐5‐EI > Bonsai. The magnitude of differences in drought avoidance characteristics among cultivars (least cuitivar = 100% base) for each year, respectively, were 213 (1991) to 200% (1992) for late summer root length density (RLD) at 20‐ to 60‐cm depth; 182 (1991) to 173% (1992) for total root length (TRL) lat e summer; and127%for evapotranspiration (ET) averaged over all water use periods (i.e., 1991 and 1992). Field measured ET rates revealed much lower ET rates (33–73% less) for the combination of humid climate and mild drought stress than reported in the literature for semi‐arid/arid and well‐irrigated tall fescue. Additionally, multiple regression analysis demonstrated that high RLD (20‐ to 60‐cm depth) was associated with less LF and wilt; maintenance of ET at 4 to 8 d after irrigation was related to less LF; and high RLD (3‐ to 10‐cm depth) related to greater LF and wilt. This suggests that high RLD in the deeper root zone and the ability to maintain ET as the soil dries are important for drought resistance of tall fescues.

Endophyte infection effects on stomatal conductance, osmotic adjustment and drought recovery of tall fescue.

Presence of the endophytic; fungus Acremonium coenophialum Morgan-Jones and Gams in tall fescue (Festuca artuidinacea- Sehreb.) enhances host persistence in drought-prone environments. However, the physiological mechanism is not well understood. We investigated the influence of endophyte infection and water deficit on osmotic adjustment, stomatal conductance, tiller survival and leaf elongation rate of genotype GA87-122 and cv. Kentucky-31 (KY31) of tall fescue. Plants were grown in a greenhouse in pots containing fine-silty topsoil (experiment 1) or sand (experiment 2). In expt 1, endophyte-infected (EI) and endophyte-free (EF) isolines of GA87-122 were exposed to two drought preconditioning cycles, after which all pots were re-watered and osmotic adjustment determined. Osmotic adjustment was -0.46 and -0.51 MPa in El leaf blades and tiller bases and -0.29 and -0.13 MPa in EF leaf blades and tiller bases, respectively. In expt 2, EI and EF GA87-122 and KY31 Mere exposed to severe drought after two preconditioning cycles, then re-watered. During the second preconditioning drying cycle of KY31, stomatal conductance tended to be lower in EI than in EF plants, but the difference was significant (P⩽ 0-05) only at two sampling times. Shoot tissues osmotically adjusted 0.17-0.31 MPa more in EI than in EF plants. Tiller survival and leaf elongation rates were higher (P⩽ 0.05) in preconditioned EI than in EF plants. Basal-zone osmotic adjustment was correlated with tiller survival rate in GA87-122 and KY31 (r = 0.87, P⩽ 0.01 for both). Enhanced osmotic adjustment in the meristematic and growing zone might account far improved survival of tillers by facilitating protection of the apical meristem.

Alteration of Phenotypic Variances by the Endophyte of Tall Fescue

Widespread infection of tall fescue (Festuca arundinacea Schreber) by the endophytic fungus (Acremonium coenophudum Morgan‐Jones and Gams) is responsible for poor performance of grazing animals. Because infection results in changes in phenotypic means for numerous traits, changes in phenotypic variances could also be a result of infection. Phenotypic variances for forage and seed production were investigated in studies of polycross families from endophyte‐infected (El) and endophyte‐free (EF) clones of 20 tall fescue genotypes. No significant phenotypic variance for forage production was detected among El families during the study. In 1989, phenotypic variances for EF were greater than El for both harvests, suggesting that the endophyte can mask plant genotypic variance. Significant phenotypic variances were observed for all seed production traits in both El and EF. Phenotypic variances for total seed weight and seed numbers in 1990 were greater for El than for EF. Estimates of genetic variance for these traits were not greater than twice the standard error in the EF state but were greater than twice the standard error in the El state. The resulting heritability estimates reflected this difference. Endophyte presence could result in overestimates of plant genotypic variance for these traits. Breeding strategies should consider presence or absence of endophyte and the possible effects on variances.

Oviposition and development of face flies in dung from cattle on herbage and supplemented herbage diets

Dung was collected from Angus cattle (Bos taurus L.) fed (ad libitum) hays of endophyte-free (EF) and endophyte (Acremonium coenophialum Morgan-Jones and Gams) infected (EI) tall fescue (Festuca arundinacea Schreb.), smooth bromegrass (Bromus inermis Leyss.), red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.), and alfalfa-smooth bromegrass (1:1 w/w) and green-chopped Kentucky bluegrass (Poa pratensis L.). Samples of dung were subsequently collected from the same animals offered the same herbage diets supplemented each day with ground maize (Zea mays L.) kernels at 0.35 kg per body weight. Dung from both sources were used in bioassays to establish oviposition preferences of face flies (Musca autumnalis De Geer). When offered dung from herbage diets, face flies deposited 38.3% of their eggs on dung derived from EF tall fescue diets, 9.9% on dung from EI tall fescue diets, 21.0% on dung from alfalfa diets, 7.4% on dung from red clover diets and 22.8% on dung from alfalfa-bromegrass diets. Face flies avoided ovipositing in dung from cattle ingesting bromegrass hay and Kentucky bluegrass green-chop. Supplements increased oviposition preference of face flies for dung from cattle ingesting Kentucky bluegrass greenchop to 19.1% at the expense of oviposition on dung from cattle ingesting alfalfa hay diets (4.5%), otherwise, they had little effect on oviposition preference ranking. Growth and development of first instar larvae of face flies was also measured in bioassays of dung from cattle on herbage and supplemented herbage diets. The presence of endophyte reduced pupation in dung from cattle on tall fescue hay diets from 86.3 to 79.8% and from 90.1 to 73.2% in dung from cattle on supplemented tall fescue hay diets. Pupal liveweights averaged 27.5 mg on dung from cattle on EF tall fescue diets, 22.1 mg from dung of cattle on EI tall fescue diets, 22.2 mg from dung of cattle on supplemented EF tall fescue diets and 24.0 mg from dung of cattle on supplemented EI tall fescue diets. Eclosion and the sex ratio of adults were not affected by dung from cattle on different source diets.

Yield and Persistence of Tall Fescue in the Southeastern Coastal Plain after Removal of Its Endophyte

AbstractThe coastal plain of the southeastern USA lacks a dependable perennial cool season forage crop, but tall fescue (Festuca arundinacea Schreb.) germplasms have been developed which show greater persistence and yield than currently marketed cultivars in this region. Since these germplasms were found to be infected with the tall fescue endophyte (Acremonium coenophialum Morgan‐Jones and Gams), the contribution of the endophyte to their performance was unknown. The objective of this study was to compare yield and stand survival of endophyte‐infected (El) and endophyte‐free (EF) (achieved by removal of its endophyte) versions of four persistent germplasms (GA‐5, GA‐Jesup, GA‐Jesup Improved, and GA‐Ecotype KY31) in clipped small plots at three locations in Georgia (Americus and Tifton in the coastal plain and Watkinsville located in the fescue growing area of the southern piedmont region) for a 3‐yr period. The El version of each germplasm showed greater stand survival and yield than its EF version at Americus and Tifton, but no differences were recorded for infection status for the same parameters at Watkinsville. These findings indicate that endophyte removal greatly reduces the ecological fitness of tall fescue by possibly allowing less tolerance to summer drought. Presently, only El tall fescue can be dependably recommended for perennial pasture in the southeastern coastal plain.

A preliminary study of growth, serum prolactin and reproductive performance of beef heifers grazing [formula omitted][formula omitted]-infected tall fescue

In an experiment with a 2×2 factorial arrangement of treatments, 32 virgin Angus heifers were used to study effects of tall fescue endophyte Acremonium coenophialum and energy supplementation on reproductive performance. Treatments were feeding of endophyte-free (EF) or endophyte-infected (EI) tall fescue without (0%) and with energy supplementation at one percent group mean body weight (1%). Blood samples were collected at 28-day intervals for prolactin (PRL). Starting 21 days before the breeding season, blood was also collected weekly for progesterone (P 4) and PRL. After 99 days of grazing, heifers received Syncro-Mate-B (SMB) and were then artificially inseminated over a 30-day period. Heifers on EI-0% had a lower (P<0.05) average final body weight. Highest average daily gain was observed in heifers fed EF-1% (0.98 kg/day), whereas, heifers fed EI-0% had lowest average daily gain (0.53 kg/day; P<0.05). Endophyte-infected fescue depressed serum PRL concentrations (171 and 143 ng/ml vs 70 and 85 ng/ml; EF-0% and EF-1% vs EI-0% and EI-1%, respectively; P<0.05). No differences were observed among treatments in luteal activity before or after SMB, in pregnancy rates after a synchronized estrus or in overall pregnancy rates during the 30-day breeding season. Endophyte-infected fescue decreased average daily gain and depressed serum concentrations of prolactin, but had no effect on reproductive performance as measured in this study.

Field Screening for Rhizome Number in Tall Fescue

Rhizomes can enhance competitiveness and persistence of tall rescue, Festuca arundinacea Schreber., but reliable field screening techniques need to be developed for the rhizome trait. We investigated the effects of plant age and infection with the endophyte Acremonium coenophialum (Morgan‐Jones &amp; W. Gams) [previously Epichloe typhina (Fries.) Tulasne] on number of rhizomes. Six, endophyte‐infected (EI) genotypes varying in ability to produce rhizomes and their endophyte‐free (EF) clones were compared in a split‐split plot design with plant age (about 3, 6, 9, and 12 mo after transplanting) as main plots, genotypes as subplots, and infection status as sub‐subplots. The experiment was planted twice and rhizomes counted on each treatment in the field at the time of digging and after washing. Number of rhizomes was highest 1 yr after transplanting. More rhizomes were counted on washed than field‐counted plants, but correlations between the two were high (r = 0.95), indicating that either would accurately rank genotypes. There was no endophyte effect on number of rhizomes, but a significant genotype × infection status interaction was found in March. Screening within a closed EI or EF population and counting rhizomes on freshly dug l‐yr‐old plants at one location is projected to be a good procedure. When this procedure was used estimate heritability for number of rhizomes within EF ‘Kentucky 31’, a broad‐sense estimate of 0.76 and narrow‐sense estimates ranging from 0.38 to 0.88 were calculated.

Nitrogen Effects on Yield and Forage Quality of Perennial Ryegrass and Tall Fescue

AbstractNegative animal effects of tall fescue (Festuca arundinacea Schreb.) infected (EI) with the endophytic fungus Acremonium coenophialum Morgan‐Jones and Gams are reduced by substituting endophyte‐ free (EF) tall fescue or other forage species. A field experiment was conducted on Maury silt loam (fine, mixed, mesic, Typic Paleudults) soil from 1986 to 1988 to compare forage yields and quality of ‘Kenhy’‐EF, Kenhy‐EI, and ‘Johnstone’ tall fescue with ‘Ensilo’ (diploid) and ‘Reveille’ (tetraploid) perennial ryegrass (Lolium perenne L.) and ‘Bison’ ryegrass (Lolium intermediate). Each cultivar received 0, 75, or 150 kg ha−1 of N annually. At 150 kg ha−1 of N, Johnstone produced the highest 1987 to 1988 average dry matter (DM) yields of 6.7 Mg ha−1 compared with 5.7 Mg ha−1 for Kenhy‐EI. Tall fescue generally produced higher yields than ryegrass. Ground cover after 3 yr for Reveille of 72% did not differ from Kenhy‐EI (79%), but Ensilo (61%) and Bison (31%) were lower. Endophyte effects on yield and quality of Kenhy were seldom significant. Two‐year weighted average in vitro dry matter disappearance (IVDMD) values were 685, 663, 626, 628, and 641 g kg−1 for Reveille, Ensilo, Kenhy‐EF, Kenhy‐EI, and Johnstone, respectively. Increasing N levels increased N concentration of tall fescue but did not consistently affect that of ryegrass. These results indicate that some cultivars of ryegrass can persist at this location, but that summer productivity is well below that of tall fescue. However, some potential may exist for germplasm improvement of perennial ryegrass based on existing cultivars. Endophyte effects on yield and quality of Kenhy tall fescue under the conditions of this study were small.

Yield, Digestibility, and Chemical Composition of Endophyte Free and Infected Tall Fescue

AbstractUtilization of low‐endophyte (Acremonium coenophialum Morgan‐Jones and Gams) cultivars of tall fescue (Festuca arundinacea Schreb.) has been shown to improve animal performance; however, insufficient information is available on the direct effects of endophyte infection on the productivity and composition of tall fescue herbage. A 2‐yr field study was conducted to assess the effects of A. coenophialum infection on the yield, digestibility, and chemical composition of tall fescue. Endophyte‐free (EF) and endophyte‐infected (EI) plots for each of two tall fescue cultivars (Kenhy and Kentucky 31) were established in August 1985 on a Maury silt loam (fine, mixed, mesic Typic Paleudalt) soil. Dry matter yields were determined for three harvests made in 1986 and 1987. Total N, fiber composition, and in vitro rate and extent of neutral detergent fiber (NDF) digestion were determined on samples of first and second harvest forage. Dry matter yields were not affected by infection status and averaged 0.80 and 0.83 Mg ha−1 in 1986 and 1.69 and 1.79 Mg ha−1 in 1987 for EF and EI tall fescue, respectively. Endophyte infection status had no effect on the rate or extent of NDF digestion. Rate of NDF digestion averaged 0.056 and 0.055 h−1 for EF and El tall fescue, respectively. Endophytic infection also had no influence on the N concentration or fiber composition of tall fescue. The results of this study suggests that A. coenophialum does not have a significant effect on the digestibility or chemical composition of tall fescue.

Effects of feeding endophyte-infected fescue hay on portal and hepatic nutrient flux in steers.

Six Holstein steers (313 +/- 10 kg BW) surgically fitted with hepatic portal, mesenteric venous, mesenteric arterial, and hepatic venous catheters were used in a replicated crossover design experiment to evaluate the feeding of Acremonium coenophialum-infected fescue hay on portal-drained visceral and hepatic nutrient metabolism. Only four steers had functional hepatic catheters. Infected (INF) and endophyte-free (EF) fescue hays were harvested on the same day in May, at the soft dough stage of maturity, from a similar location in southeast Kansas. The hay was chopped through a 2.5-cm screen and fed in 12 portions daily. Intake was limited to 5.2 kg of DM/d to equalize consumption. Each experimental period lasted 21 d. Dietary CP concentration was greater for INF than for EF (9.9 vs 8.6%); however, apparent digestibilities of DM (52.6%) and N (37%) were not different. Ruminal total VFA concentrations and molar proportions were not different with the exception of butyrate, which was increased (P less than .10) for steers when they were fed INF. Feeding of INF increased (P less than .05) arterial beta-hydroxybutyrate concentration and decreased (P less than .10) arterial butyrate concentration. Steers fed EF showed a greater (P less than .05) portal-arterial concentration difference for acetate and an increased (P less than .05) net portal flux of acetate (500 vs 620 mmol/h). No differences in net flux were noted for any of the other VFA, glucose, lactate, urea N, insulin, glucagon, or prolactin.(ABSTRACT TRUNCATED AT 250 WORDS)